Production of palmitic acid



Patented June 29, 1954 PRODUCTION OF PALMITIC ACID Hans GeorgeKirschenbauer, Allendale, N. L, as-

signor to Colgate-Palmolive Company, Jersey City, N. J., a corporationof Delaware No Drawing. ApplicationJanuary 31, 1951,

. 1 Serial No. 208,835

11 Claims.

Palmitic acid isan excellent raw material for the manufacture of soap,particularly hard soaps. It is also employed as an intermediate inmaking compounds suitable for many other industrial uses. It is presentin rather substantial quantities among the component acids of manyvegetable and animal oils including other fatty acids of an unsaturatednature such as oleic and linoleic. Tall oil obtained as a byproductderived from the waste liquor of pine oil pulp is a rich sourceofpalmitic acid but this type of oil contains not only palmitic acid butother miscellaneous acids in solution therewith. Processes have beenused for treatment of oil such as tall oil to produce palmitic acid. Onesuch process is known as the Varrentrapp reaction, which per se has beenknown to chemists since about 1841. This reaction involves heating thevegetable oil containing the fatty acid radicals (such as the oleic acidradical) which it is designed to convert to palmitic acid in thepresence of excess caustic such as KOI-I or NaOI-I. The temperature ofheating is preferably of the order of about 320 C. when substantiallyanhydrous conditions are employed, but may be appreciably lower, such asof the order of about 260 0., if carried out in an autoclave in thepresence of a substantial quantity of water. The conversion of the oleicto palmitic acid is accompanied by the generation of hydrogen.

It has been found that if the fatty oil used as a starting material in aprocess of the above-mentioned nature contains glyceride esters of otherunsaturated acids besides oleic, such as linoleic, linolenic and similarunsaturated acids, the attempted conversion to palmitic acid is verysmall because in such cases the more highly unsaturated'acids are brokendown to saturated acids of shorter chain length, such as myristic fromlinoleic and lauric from linolenic acid.

It is therefore an object of this invention to provide a process whichsubstantially increases the yields of the relatively more desirablepalmitic acid resulting from the treatment of vegetable oils in theaforesaid manner.

Generally speaking, the process comprises two steps. First, thevegetable oil starting material is seletcively hydrogenated underconditions such that the relatively more highly unsaturated fatty acidssuch as linoleic and linolenic acids normally present therein arelargely 01 substantially completely converted to oleic acid without atthe same time substantially affecting the oleic acid content; andsecond, the product of the selective hydrogenation is subjected to theVarrentrapp reaction to convert the oleic acid component to the desiredpalmitic acid. The polyunsaturated fatty acids such as linoleic andlinolenic acids are hydrogenated during the selective hydogenation stepto an oleic acid that may be present as such or in one or more of itsisomeric forms, while at the same time the oleic acid originally presentin combination as glycerides in the starting material remainssubstantially unaffected. The selectively hydrogenated material, inwhich most of the acids that were morehighly unsaturated than oleic havebeen converted to oleic acids, is then subjected to a heat treatment inthe presence of excess alkali such as caustic potash or caustic soda,whereupon the resultant product consists essentially of a relativelyhigh percentage of palmitic acid soap resulting from the Varrentrappreaction, which is conjectured as involving the migration of the doublebond of the oleic acid toward the 16,117 position with subsequentcracking of the fatty acid between C16 and Cu to give the desired (hesaturated acid component as a major reaction product.

In order to indicate still more fully the nature of the presentinvention, the following examples of typical procedure are set forthwith the understanding that this is by way of illustration only, and notby way of limiting the scope of the invention.

Example I An example of the process, carried out under substantiallyanhydrous conditions, is as follows:

A cottonseed oil containing as component acids the following: 20%palmitic, 30% oleic, 45% linoleic and 5% miscellaneous acids includingsome linolenic acid, is subjected to selective hydrogenation in order toconvert the linoleic and linolenic acids present into oleic acids. Byselective hydrogenation, it is to be understood that the conditions ofhydrogenation under otherwise conventional conditions are carefullycontrolled so as to terminate the hydrogenation when substantially allthe polyunsaturated acids have been converted to the monounsaturatedoleic acid. The selective hydrogenation may be carried out atatmospheric or slightly elevated pressures, using known nickelhydrogenation catalysts of the selective type such as are commerciallyavailable. The temperatures of hydrogenation are preferably of the orderof (3., although variations somewhat on either end of this range may beresorted to without sace rificing all the advantages thereof.

Following the selective hydrogenation step, the hydrogenation catalystis removed and the material is then subjected to reaction with excesscaustic alkali, such as caustic soda or caustic potash or mixturesthereof, at elevated temperatures such as of the order of 300400 C.although preferably temperatures near the lower end of this range, suchas 320 C., are employed. This results in a high yield of an alkali metalsoap of palmitic acid. Upon separating this soap from the crude reactionmixture, and acidifying the soap, a water-insoluble fatty acid mixtureis obtained which contains about 90 palmitic acid.

Example II An example of the process, carried out under hydrousconditions, is as follows:

A corn oil having an iodine value of 126.4, and in which the major acidcomponents are 8% palmitic, 4% stearic, 45% oleic, 41% linoleic and 2%miscellaneous, is subjected to selective hydrogenation at 165 0., usinga conventional selective-type nickel hydrogenation catalyst in ahydrogenating vessel of the shaking type at a pressure slightly above 10atmospheres. When the iodine value ofthe corn oil is substantiallylowered, namely, to a value corresponding to that for the substantiallycomplete conversion of the polyunsaturated acid components tomonounsaturated acid components (i. e., to an iodine value of 70.8), theselective hydrogenation is discontinued. The hydrogenation catalyst isremoved by filtration and 100 parts of the selectively hydrogenated cornoil product is transferred to a reaction vessel provided with externalheating means and equipped with agitating means. 50 parts of an aqueouspotash lye containing approximately parts of anhydrous KOH are thenadded to the contents of this vessel. ture is gradually increased to 320C.', to eliminate the water from the reaction mixture. To the moltenmixture there is now added with constant agitation 150 parts of powderedanhydrous KOH. Heating is continued for 2 hours after all of the caustichas :been added. The reaction mixture is cooled and taken up in about400 parts of water. The grained-out soap, consisting principally ofpotassium palmitate is recovered by skimming, leaving the bulk of theunreacted caustic as well as the major portion of the potassium acetateproduced during the Varrentrapp reaction in the lower aqueous layer. Thesoap thus obtained may be used, as such, or if desired it may be readilyconverted to palmitic acid by acidification followed by distillation.The potassium palmitate reaction product is obtained in high yield.

Other vegetable and animal oils having a substantial content ofpolyunsaturated acids of 18 carbon atoms or more, such as palm, soybean, perilla, peanut, avocado, olive, olive oil foots and red oil, aresuitable as starting materials. Also, any higher fatty acid mixture ofsuitable composition may be employed ncluding soap stocks and acidulatedsoap stocks, or any other suitable higher fatty acid mixtures obtainedby known processes, so long as these contain the polyunsaturated acidsas just mentioned. Additionally, any known technique for obtaining highselectivity during hydrogenation in converting linoleic or linolenicacid to oleic acids may be used. Additionally, any suitable alkalibesides caustic potash may be used such as caustic soda or mixtures ofthe two. The combination of selective hydrogenation and the Varrentrappre- The mixture is agitated and the temperaaction results surprisinglyin high yields of palmitic acid. The combination of the two steps thusprovides industry with a process which is very efiicient and whicheliminates the disadvantages in the processes already known in the art.The major disadvantage of all prior art processes was that the finalproduct was relatively low in palmitic acid and relatively high in theshorter chain degradation products of the original fatty oil material.The present process on the other hand gives high yields of palmitic andlow yields of the less desired shorter chain degradation products.

While specific examples of preferred methods embodying the presentinvention have been set forth above, it will be apparent that manychanges and modifications may be made in the methods of procedurewithout departing from the spirit of the invention. It will therefore beunderstood that the examples cited and the particular proportions andmethods of operation set forth above are intended to be illustrativeonly, and are not intended to limit the scope of the inven-' tion.

-What is claimed is:

1. In a process for the production of palmitic acid from a fattymaterial containing polyunsaturated soap-forming fatty acid components,the steps that comprise selectively hydrogenating the fatty material tohydrogenate the polyunsaturated fatty acid components to oleic acidcomponents, heating the resulting product containing oleic acidcomponents produced by the selective hydrogenation to an elevatedtemperature in the presence of excess alkali to convert said oleic acidmaterial to palmitic acid material, and recovering a palmiticacid-containing reaction product from the reaction mixture.

2. In a process for the production of palmitic acid from a fatty oilmaterial containing high molecular weight polyunsaturated soap-formingfatty acid components of which the fatty acid radicals are of 18 carbonatom chain length, the steps that comprise selectively hydrogenating thefatty oil material to hydrogenate the polyunsaturated fatty acidcomponents to oleic acid components, heating the resulting selectivelyhydrogenated product containing oleic acid components produced by theselective hydrogenation to a temperature of about 260 to 400 C. in thepresence of excess alkali to convert said oleic acid material topalmitic acid material, and recovering a palmitic acid-containingreaction product from the reaction mixture.

3. in a process for the production of palmitic acid from a fatty oilmaterial containing oleic acid and more highly unsaturated soap-formingfatty acid components of the group consisting of linoleic and linolenicacids, the steps that comprise selectively hydrogenating the fatty oilmaterial to hydrogenate the more highly unsaturated fatty acidcomponents to oleic acid components without substantially furtherhydrogenating the latter, heating the resulting selectively.hydrogenated product containing oleic acid components produced by theselective hydrogenae tion in admixture with the originally present oleicacid components to an elevated temperature in the presence of excesscaustic alkali to convert said oleic acid material to palmitic acidmaterial, and recovering a palmitic acid-containing reac-' tion productfrom the reaction mixture.

4. In a process for the productionof palmitic acid from a fatty oilmaterial comprising glyceride esters of oleic, linoleic and linolenicacids,

the steps that comprise selectively hydrogenating the fatty oil materialin the presence of a selective hydrogenation nickel catalyst tohydrogenate the glyceride esters of linoleic and linolenic acids toglyceride ester of oleic acid, heat ing the selectively hydrogenatedproduct containing augmented oleic acid produced by the selectivehydrogenation to a temperature of about 260 to 400 C. in the presence ofexcess alkali to convert said oleic acid material to palmitic acidmaterial, and recovering a palmitic acid-containing reaction productfrom the reaction mixture.

5. A process for the production of palmitic acid that comprisesselectively hydrogenating a vegetable oil containing fatty acids thereinto hydrogenate only the more highly unsaturated fatty acids therein toan oleic acid, heating the selectively hydrogenated product in thepresence of excess alkali to convert oleic acid to palmitic acid soap,and acidifying the resultant reaction product to produce palmitic acid.

6. A process for the production of palmitic acid that comprisesselectively hydrogenating a fatty acid mixture containing an oleic acidtogether with acids more highly unsaturated than oleic acid tohydrogenate only said more highly unsaturated acids to an oleic acid,heating the selectively hydrogenated product in the presence of excessalkali to convert oleic acid to palmitic acid soap, and acidifying theresultant reaction product to produce palmitic acid.

'7. A process for the production of palmitic acid that comprisesselectively hydrogenating a cottonseed oil to hydrogenate the morehighly unsaturated fatty acids therein to an oleic acid,

heating the selectively hydrogenated product in the presence of excessalkali to convert said oleic acid material to palmitic acid soap, andacidifying the resultant reaction product to produce palmitic acid.

8. A process for the production of palmitic acid that comprisesselectively hydrogenating a cottonseed oil to hydrogenate the morehighly unsaturated fatty acids therein to an oleic acid,

heating the selective hydrogenated product to about 300 to 320 C. in thepresence of excess caustic potash to convert said oleic acid material topotassium palmitate, and acidifying the resultant reaction product toproduce palmitic acid.

9. A process for the production of palmitic acid that comprisesselectively hydrogenating a vegetable oil containing an oleic acidtogether with acids more highly unsaturated than oleic acid toselectively hydrogenate only the more highly unsaturated acids to anoleic acid, heating the selectively hydrogenated product in the presenceof excess alkali to convert said oleic acid material to palmitic acidsoap, and acidifying the resultant reaction product to produce palmiticacid.

10. A process for the production of palmitic acid that comprisesselectively hydrogenating a vegetable oil containing an oleic acidtogether with acids more highly unsaturated than oleic acid toselectively hydrogenate only the more highly unsaturated acids to anoleic acid, heating the selectively hydrogenated product in the presenceof excess caustic potash to convert said oleic acid material topotassium palmitate, and acidifying the resultant reaction product toproduce palmitic acid.

11. A process for the production of palmitic acid that comprisesselectively hydrogenating a cottonseed oil containing an oleic acidtogether with acids more highly unsaturated than oleic acid, includinglinoleic and linolenic acids, to hydrogenate only the more highlyunsaturated acids to an oleic acid, heating the selectively hydrogenatedproduct in the presence of excess caustic potash to convert said oleicacid material to potassium palmitate, and acidifying the resultantreaction product to produce palmitic acid.

References Cited in the file of this patent UNITED STATES PATENTS Swernet al Dec. 28, 1948

1. IN A PROCESS FOR THE PRODUCTION OF PALMITIC ACID FROM A FATTYMATERIAL CONTAINING POLYUNSATURATED SOAP-FORMING FATTY ACID COMPONENTS,THE STEPS THAT COMPRISE SELECTIVELY HYDROGENATING THE FATTY MATERIAL TOHYDROGENATE THE POLYUNSATURATED FATTY ACID COMPONENTS TO OLEIC ACIDCOMPONENTS, HEATING THE RESULTING PRODUCT CONTAINING OLEIC ACIDCOMPONENTS PRODUCED BY THE SELECTIVE HYDROGENATION TO AN ELEVATEDTEMPERATURE IN THE PRESENCE OF EXCESS ALKALI TO CONVERT SAID OLEIC ACIDMATERIAL TO PALMITIC ACID MATERIAL, AND RECOVERING A PALMITICACID-CONTAINING REACTION PRODUCT FROM THE REACTION MIXTURE.